With the game still goalless going into the final minute of normal time it looked like United would have to settle for a disappointing draw against Leyton Orient after failing to find the form that swept Brighton away on Saturday.
But up popped super-sub Gradel with a brilliant spin to find space just inside a crowded penalty box and he then lashed an unstoppable shot into the roof of the net for a spectacular goal good enough to win any game.
The inevitable chant of "sign him up" rang round the ground and for the third home league game in a row the man from Leicester City had changed a game badly in need of lifting.
Right from his first run with the ball and a nutmeg on left-back Charlie Daniels, Gradel lit up Elland Road and after coming on as a 62nd minute substitute for disappointing striker Sam Vokes he gave Leeds what they had been missing for the previous hour - a player who could run at opponents and cause danger.
He went close to scoring twice before his eventual winner with an acrobatic volley that sent the ball just over and with a cross-shot that was turned over by keeper Jamie Jones.
Another second half United substitute, Aidan White, also gave an eye-catching performance after coming on for the injured Andrew Hughes, but there was little else to enthuse about the rest of this display as the Whites looked anything but league leaders for much of the contest.
They only managed one shot on target in the whole of the first half - and that a tame Jonny Howson effort - although they did push Orient back after the break without creating many clear chances.
Vokes fluffed one good opportunity when well placed in the box and another of the disappointments on the night, Robert Snodgrass, saw his weak shot easily blocked, but it was the visitors who looked more likely to score in the opening 45 minutes.
Sean Thornton hit a shot wide when well placed, Scott McGleish was denied by a good block by Hughes and speedy winger Andros Townsend, who terrorised home right-back Leigh Bromby, forced a save from Casper Ankergren with a well struck shot from distance.
However, the Orient threat subsided in the second half and their time wasting tactics backfired when Leeds came up with their late winner to stay six points clear at the top.
Match facts
Leeds United 1
(Gradel 89)
Leyton Orient 0
Tuesday, November 24, 2009
Coca-Cola League One
Att: 19,744
Leeds: Ankergren, Bromby, Michalik, Kisnorbo, Hughes (White 47), Howson (Grella 81), Kilkenny, Doyle, Snodgrass, Vokes (Gradel 61), Beckford.
Leyton Orient: Jones, Purches, Chorley, Mkandwrie, Daniels, Smith, Chambers, Thornton, Summerfield (Jarvis 90), Townsend, McGleish (Scowcroft 59).
Referee: D Foster.